f0rki / catatonit Goto Github PK

A container init that is so simple it's effectively brain-dead. This is a rewrite of initrs in C, because we found that it is not possible to statically compile Rust binaries without using musl. That was, in turn, a reimplementation of other container inits like tini and dumb-init.

The reason for re-implementing docker-init is because it appears as though all of the other implementations do not handle signals as correctly as they should. In particular, they all appear to make use of sigwait(2) (tini does a sigtimedwait(2) for an interval and then will do a waitpid(2) even if it didn't detect a SIGCHLD). catatonit uses signalfd(2), which has its own warts, but the improvements over sigwait(2) are significant in terms of stability. Ideally we would just write a patch for the other projects to use signalfd(2) rather than creating a new project, but after some time spent looking at tini and dumb-init we felt that such patches would be closer to full rewrites.

In addition, the purpose of catatonit is to only support the key usage by docker-init which is /dev/init -- <your program>. With few exceptions, no other features will be added.

catatonit has identical usage to other basic docker-init's -- you give it the command and list of arguments to that command. If catatonit is not pid1, it will try to use the sub-reaper support in the kernel. You can pass -g if you want signals to be forwarded to the entire process group of your spawned process (otherwise it's just forwarded to the process spawned).

If you wish to use catatonit as a convenient pause container (do not spawn a child process nor do any signal handling), use pass -P.

catatonit uses autotools for building, so building is a fairly standard:

% ./autogen.sh
% ./configure
% make
% sudo make install

catatonit is licensed under the GNU General Public License version 2 or later.

catatonit: a container init so simple it's effectively brain-dead
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